Metal-and-resin composite and method for making  the same

ABSTRACT

A metal-and-resin composite includes an aluminum or aluminum alloy substrate, an aluminum oxide film on the aluminum or aluminum alloy substrate, and at least one resin article coupled to the aluminum oxide film. The aluminum or aluminum alloy substrate defines a plurality of corrosion pores, and the aluminum oxide film defines a plurality of nano-pores. Some of the nano-pores extend through the aluminum oxide film and couple to the corrosion pores. Some parts of the resin article fill in the nano-pores and the corrosion pores, thus greatly improving bond between the resin article and the aluminum or aluminum alloy substrate.

FIELD

The subject matter herein generally relates to a metal-and-resin composite and a method for making the metal-and-resin composite.

BACKGROUND

Many people use portable electronic devices such as mobile phones and personal digital assistants (PDAs). Housings of the portable electronic devices may be made of two or more different materials, such as aluminum alloy and resin. There is a need to combine aluminum alloy and resin.

BRIEF DESCRIPTION OF THE DRAWINGS

Implementations of the present technology will now be described, by way of example only, with reference to the attached figures.

FIG. 1 is a cross-sectional view of an exemplary embodiment of a metal-and-resin composite.

FIG. 2 is a scanning electron microscope (SEM) image of an exemplary embodiment of a cross-section of aluminum or aluminum alloy after electrochemical treatment.

FIG. 3 is a cross-sectional view of an exemplary embodiment of the aluminum or aluminum alloy after electrochemical treatment.

FIG. 4 is an SEM image of an exemplary embodiment of a surface of the aluminum or aluminum alloy after electrochemical treatment.

FIG. 5 is a flow chart.

FIG. 6 is a cross-sectional view of molding the composite shown in FIG. 1.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts may be exaggerated to better illustrate details and features of the present disclosure.

Several definitions that apply throughout this disclosure will now be presented.

The term “coupled” is defined as connected, whether directly or indirectly through intervening components, and is not necessarily limited to physical connections. The connection can be such that the objects are permanently connected or releasably connected. The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other word that substantially modifies, such that the component need not be exact. For example, substantially cylindrical means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series, and the like.

FIG. 1 illustrates a metal-and-resin composite 100 according to a first exemplary embodiment. The metal-and-resin composite 100 includes an aluminum or aluminum alloy substrate 11, an aluminum oxide film 13 on the aluminum or aluminum alloy substrate 11, and at least one resin article 15 coupled to the aluminum oxide film 13.

FIG. 2 illustrates an SEM image of a cross-section of the aluminum or aluminum alloy after being electrochemically treated, wherein the thin layer in the middle of FIG. 2 is an aluminum oxide film 13, the substance below the aluminum oxide film 13 is an aluminum or aluminum alloy substrate 11, and the substance above the aluminum oxide film 13 is a resin part configured to fix the sample of the aluminum or aluminum alloy substrate 11 together with the aluminum oxide film 13 during the SEM test. The aluminum oxide film 13 is thin and can have a thickness of less than 1 μm. In some embodiments, the aluminum oxide film 13 can have a thickness of about 500 nm.

FIG. 3 shows that the aluminum oxide film 13 defines a plurality of nano-pores 131, and the aluminum or aluminum alloy substrate 11 defines a plurality of corrosion pores 111 in the surface. Some nano-pores 131 extend through the aluminum oxide film 13 and couple to the corrosion pores 111 partly or completely. Thus, parts of the resin article 15 can fill in the nano-pores 131 and the corrosion pores 111 coupling to the nano-pores 131.

In the exemplary embodiment, some nano-pores 131 do not couple to the corrosion pores 111. As shown in FIG. 3, some of the nano-pores 131 do not extend through the aluminum oxide film 13, and some of the nano-pores 131 extend through the aluminum oxide film 13 and do not couple to a corresponding corrosion pore 111. As well, some corrosion pores 111 do not couple to a corresponding nano-pore 131 as shown in FIG. 3.

FIG. 4 illustrates an SEM image of a surface of the aluminum or aluminum alloy after electrochemical treatment. As shown, the nano-pores 131 are substantially evenly distributed in the aluminum oxide film 13. The nano-pores 131 have an average diameter of about 10 to about 80 nm.

The aluminum oxide film 13 with the nano-pores 131 and the corrosion pores 111 of the aluminum oxide film 13 are formed by electrochemically treating an aluminum or aluminum alloy article. The electrochemical treatment in this disclosure is substantially different from the traditional anodizing process for aluminum or aluminum alloy. In the traditional anodizing process of aluminum or aluminum alloy substrate, only a porous aluminum oxide layer having a thickness of about several micrometers to hundreds of micrometers forms on the aluminum or aluminum alloy.

The at least one resin article 15 is formed on the aluminum oxide film 13 by injection molding. The at least one resin article 15 can be made of resin selected from a group consisting of polyphenylene sulfide (PPS), polyamide (PA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), thermoplastic polyurethane elastomer (TPU), thermoplastic polyester elastomer (TPEE), polycarbonate (PC), or any combination thereof. In some embodiments, the at least one resin article 15 can also contain glass fiber. For example, when the resin is PPS, PBT, PET, or PC, the at least one resin article 15 can also contain about 30 wt % glass fiber. When the resin is PA, the at least one resin article 15 can contain about 50 wt % glass fiber.

FIG. 5 illustrates an embodiment of a method 500 for making the metal-and-resin composite 100 may include the following steps.

First, in block 51, an aluminum or aluminum alloy article is provided and degreased. The degreasing process can include dipping the aluminum or aluminum alloy article in a sodium salt water solution for about 5 to about 15 minutes. The sodium salt water solution can include sodium carbonate having a concentration of about 30 to about 50 grams per liter (g/L), sodium phosphate having a concentration of about 30 to about 50 g/L, and sodium silicate having a concentration of about 3 to about 5 g/L. The temperature of the sodium salt water solution can be about 50 to about 60 degrees Celsius (° C.) during the degreasing process. Once degreased, the aluminum or aluminum alloy article is removed from the sodium salt water solution and rinsed in water.

Then, in block 52, the aluminum or aluminum alloy article is etched using an alkaline water solution. The etching process not only can remove metal oxide film which naturally form on the surface of the aluminum or aluminum alloy article, but also can roughen the surface of the aluminum or aluminum alloy article. The etching process can include dipping the degreased aluminum or aluminum alloy article in the alkaline water solution at room temperature for about 1 to about 3 minutes. The alkaline water solution can include sodium hydroxide having a concentration of about 30 percent to about 60 percent by weight. Once etched, the aluminum or aluminum alloy article is removed from the alkaline water solution and rinsed in water.

Next, in block 53, the aluminum or aluminum alloy article is electrochemically treated to form the aluminum or aluminum alloy substrate 11 defining the corrosion pores 111 and the aluminum oxide film 13 defining the nano-pores 131 on the aluminum or aluminum alloy substrate 11. Some of the nano-pores 131 extend through the aluminum oxide film 13 and couple to the corrosion pores 111. The aluminum oxide film 13 is thin and has a thickness of less than 1 μm. The nano-pores 131 have an average diameter of about 10 to about 80 nm.

The electrochemical treatment can be carried out in an acid water solution, with the aluminum or aluminum alloy article being an anode, and a stainless steel board or a lead plate being a cathode. The acid water solution contains phosphoric acid, sulfuric acid, oxalic acid, and citric acid, wherein the phosphoric acid can have a concentration of about 100 to about 250 milliliters per liter (ml/L), the sulfuric acid can have a concentration of about 20 to about 60 ml/L, the oxalic acid can have a concentration of about 1 to about 10 ml/L, and the citric acid can have a concentration of about 0.5 to about 2.5 ml/L. The acid water solution has a temperature of about 10 to about 30° C. during the electrochemical treatment. The electric current density through the acid solution is about 0.5 to about 4 ampere per square decimeter (A/dm²). The electrochemical treatment can last for about 3 to about 15 minutes, which is considerably less time and more effective than the traditional anodizing process (about 20 to about 60 minutes). After the electrochemical treatment, the aluminum or aluminum alloy substrate 11 together with the aluminum oxide film 13 is rinsed in water and then dried.

During the electrochemical treating process, aluminum atoms in the surface of the aluminum or aluminum alloy article can undergo two different main chemical reactions. The first main reaction is that aluminum atoms react with oxygen to form aluminum oxide. As such, the aluminum oxide film 13 defining nano-pores 131 is formed. The first main reaction formula is as follows: 2H₂O−4e⁻=O₂+4H⁺, 4Al+3O₂=2Al₂O₃. The second main reaction is that aluminum atoms lose electrons to form aluminum ions in acidic solution, which makes the aluminum or aluminum alloy substrate 11 define the corrosion pores 111 in the surface. The aluminum in the positions of the crystal defects can have priority to lose electrons to form aluminum ions. The second main reaction formula is: Al−3e⁻=Al³⁺+3e⁻. Some of the nano-pores 131 extend through the aluminum oxide film 13 and couple to the corrosion pores 111. With the growth of the aluminum oxide film 13, the forming of the corrosion pores 111 would be inhibited gradually until stopping.

Finally, in block 54, at least one resin article 15 is formed on the aluminum oxide film 13 by injection molding. FIG. 6 illustrates an injection mold 20, which includes a core insert 23 and a cavity insert 21. The core insert 23 defines several gates 231 and several first cavities 233. The cavity insert 21 defines a second cavity 211 for receiving the aluminum or aluminum alloy substrate 11 together with the aluminum oxide film 13. The aluminum or aluminum alloy substrate 11 together with the aluminum oxide film 13 is located in the second cavity 211. Molten resin is injected through the gates 231 to coat the surface of the aluminum oxide film 13, fill the nano-pores 131 and the corrosion pores 111 coupling to the nano-pores 131, and fill the first cavities 233 to form the resin article 15. As such, the composite 100 is formed.

The at least one resin article 15 can be made of resin selected from a group consisting of PPS, PA, PBT, PET, TPU, TPEE, PC, or any combination thereof. In some embodiments, the at least one resin article 15 can also contain glass fiber. For example, when the resin is PPS, PBT, PET, or PC, the at least one resin article 15 can also contain about 30 wt % glass fiber. When the resin is PA, the at least one resin article 15 can contain about 50% glass fiber.

The metal-and-resin composite 100 in this disclosure has an improved bond between the aluminum or aluminum alloy substrate 11 and the resin article 15, for the parts of the resin article 15 not only fill in the nano-pores 131 of the aluminum oxide film 13, but also fill in the corrosion pores 111 of the aluminum or aluminum alloy substrate 11.

It is believed that the exemplary embodiment and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the scope of the disclosure or sacrificing all of its advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure. 

1. A metal-and-resin composite comprising: an aluminum or aluminum alloy substrate defining a plurality of corrosion pores; an aluminum oxide film on the aluminum or aluminum alloy substrate, and defining a plurality of nano-pores, some of the plurality of nano-pores extending through the aluminum oxide film and coupling to the corrosion pores; and at least one resin article coupled to the aluminum oxide film.
 2. The metal-and-resin composite as claimed in claim 1, wherein some parts of the resin article fill in the nano-pores and the corrosion pores coupling to the nano-pores.
 3. The metal-and-resin composite as claimed in claim 1, wherein the nano-pores have an average diameter of about 10 nm to about 80 nm.
 4. The metal-and-resin composite as claimed in claim 1, wherein the aluminum oxide film has a thickness of less than 1 μm.
 5. The metal-and-resin composite as claimed in claim 4, wherein the aluminum oxide film has a thickness of about 500 nm.
 6. The metal-and-resin composite as claimed in claim 1, wherein the resin article is made of resin selected from a group consisting of polyphenylene sulfide, polyamide, polybutylene terephthalate, polyethylene terephthalate, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polycarbonate, or any combination thereof.
 7. The metal-and-resin composite as claimed in claim 1, wherein the resin article is made of resin containing glass fiber, the resin is selected from a group consisting of polyphenylene sulfide, polyamide, polybutylene terephthalate, polyethylene terephthalate, polycarbonate, or any combination thereof.
 8. The metal-and-resin composite as claimed in claim 7, wherein when the resin is polyphenylene sulfide, polybutylene terephthalate, polyethylene terephthalate, or polycarbonate, the resin article comprises about 30 wt % glass fiber; when the resin is polyamide, the resin article comprises about 50 wt % glass fiber.
 9. A method for making a metal-and-resin composite, comprising: providing an aluminum or aluminum alloy article; electrochemically treating the aluminum or aluminum alloy article to form an aluminum or aluminum alloy substrate defining corrosion pores and an aluminum oxide film on the aluminum or aluminum alloy substrate, the aluminum oxide film defining nano-pores, some nano-pores extending through the aluminum oxide film and coupling to the corrosion pores; and inserting the aluminum or aluminum alloy substrate together with the aluminum oxide film in a mold and molding resin on the surface of the aluminum oxide film to form at least one resin article.
 10. The method as claimed in claim 9, wherein the nano-pores have an average diameter of about 10 to about 80 nm; and the aluminum oxide film has a thickness of less than 1 μm.
 11. The method as claimed in claim 9, wherein some parts of the resin article fill in the nano-pores and the corrosion pores coupling to the nano-pores.
 12. The method as claimed in claim 9, wherein the electrochemically treating is carried out in an acid water solution having a temperature of about 10 to about 30° C. for about 3 to about 15 minutes, the aluminum or aluminum alloy article is an anode; the acid water solution comprises phosphoric acid having a concentration of about 100 to about 250 ml/L, sulfuric acid having a concentration of about 20 to about 60 ml/L, oxalic acid having a concentration of about 1 to about 10 ml/L, and citric acid having a concentration of about 0.5 to about 2.5 ml/L; the electric current density through the acid solution is about 0.5 to about 4 A/dm².
 13. The method as claimed in claim 9, further comprising a step of etching the aluminum or aluminum alloy article using an alkaline water solution before electrochemically treating the aluminum or aluminum alloy article.
 14. The method as claimed in claim 13, wherein the etching step is carried out by dipping the aluminum or aluminum alloy article in a sodium hydroxide water solution having a concentration of about 30% to about 60% by weight for about 1 to about 3 minutes.
 15. The method as claimed in claim 13, further comprising a step of degreasing the aluminum or aluminum alloy article using a sodium salt water solution before etching the aluminum or aluminum alloy article.
 16. The method as claimed in claim 15, wherein the degreasing step is carried out by dipping the aluminum or aluminum alloy article in a sodium hydroxide water solution for about 5 to about 15 minutes, the sodium salt water solution comprises sodium carbonate having a concentration of about 30 to about 50 g/L, sodium phosphate having a concentration of about 30 to about 50 g/L, and sodium silicate having a concentration of about 3 to about 5 g/L.
 17. The method as claimed in claim 9, wherein the resin article is made of resin selected from a group consisting of polyphenylene sulfide, polyamide, polybutylene terephthalate, polyethylene terephthalate, thermoplastic polyurethane elastomer, thermoplastic polyester elastomer, polycarbonate, or any combination thereof.
 18. The method as claimed in claim 9, wherein the resin article is made of resin containing glass fiber, the resin is one selected from a group consisting of polyphenylene sulfide, polyamide, polybutylene terephthalate, polyethylene terephthalate, or polycarbonate.
 19. The method as claimed in claim 18, wherein when the resin is polyphenylene sulfide, polybutylene terephthalate, polyethylene terephthalate, or polycarbonate, the resin article comprises about 30 wt % glass fiber; when the resin is polyamide, the resin article comprises about 50 wt % glass fiber.
 20. A method for making a metal-and-resin composite, comprising: providing an aluminum or aluminum alloy article; electrochemically treating the aluminum or aluminum alloy article to form an aluminum or aluminum alloy substrate defining corrosion pores and an aluminum oxide film on the aluminum or aluminum alloy substrate, the electrochemically treating being carried out in an acid water solution, the acid water solution comprising phosphoric acid having a concentration of about 100 to about 250 ml/L, sulfuric acid having a concentration of about 20 to about 60 ml/L, oxalic acid having a concentration of about 1 to about 10 ml/L, and citric acid having a concentration of about 0.5 to about 2.5 ml/L, the aluminum oxide film having a thickness of less than 1 μm, the aluminum oxide film defining nano-pores, some nano-pores extending through the aluminum oxide film and coupling to the corrosion pores; and inserting the aluminum or aluminum alloy substrate together with the aluminum oxide film in a mold and molding resin on the surface of the aluminum oxide film to form at least one resin article. 